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Active matrix display driving circuit

a driving circuit and active matrix technology, applied in the direction of instruments, static indicating devices, etc., can solve the problems of limited size (5 inches, much more complex process, serious damage to image uniformity), etc., and achieve the effect of improving image defects

Active Publication Date: 2005-09-15
WINTEK CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] The main purpose of this invention is to solve the said problems. This invention not only improves image defects resulting from uneven characteristics of TFT and IR drop, but also solves the problem of long charge / discharge times for low current inputs.

Problems solved by technology

The manufacturing procedure of a PM-EL display is simpler in comparison and less costly; however, it is limited in its size (<5 inches) because of its driving mode and has a lower-resolution display application.
Although LTPS-TFT possesses higher carrier mobility and higher mobility means more current can be supplied, the process is much more complex.
Images of erroneous gray scale will show up on OLED panel and seriously damage image uniformity.
The most urgent problem of the AM-EL display to be solved currently is how to reduce the impact of uneven LTPS-TFT characteristics.
Thus, there was a defect of long charge / discharge times for the capacitor and the parasitical capacitor at low current input.
The common problem for the circuits above is the voltage discharged from the storage capacitor to the gate and source of the driving transistor (Vgs) has to be less than the threshold voltage (Vth) of the driving transistor.
Nevertheless, Vgs is larger than Vth due to long discharging time.
Consequently, EL device illuminates via a small current and therefore the contrast of the display panel is not good.
Defects of this driving method are capacitance precision and impose strict requirements for capacitor processing and layout.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

embodiment 1

[0031] Refer to FIG. 1 for the circuit of a pixel of embodiment 1 in this invention. As the Figure shows: the driving circuit of each pixel on the display panel includes one scan line 10 and one data line 20 as follows:

[0032] Gates (G) of a first scan transistor TI and a second scan transistor T2 connected to one scan line 10 and source (S) connected to a data line 20.

[0033] Source (S) of a driving transistor T3 connected to VDD. Source (S) of connect transistor T4 connected to drains (D) of driving transistor T3 and second scan transistor T2 and gate (G) connected to one emission line 30.

[0034] Source (S) of a first switch transistor T5 connected to first voltage supply V1 and gate (G) connected to scan line 10. Source (S) of a second switch transistor T6 connected to second voltage supply V2 and gate (G) connected to emission line 30. The above first scan transistor T1, second scan transistor T2, driving transistor T3, connect transistor T4, first switch transistor T5 and secon...

embodiment 2

[0050] Refer to FIG. 2 for the circuit of a pixel of embodiment 2 in this invention. As the Figure shows, the driving circuit of each pixel on the display panel includes one scan line 10 and one data line 20. The driving circuit in this embodiment is about the same as that in Embodiment 1; however, the only difference is source (S) of first switch transistor T5 connected to emission line 30 instead of first voltage supply V1 and source (S) of second switch transistor T6 connected to scan line 10, not second voltage supply V2.

[0051] Actuation procedures of Embodiment 2 are described as follows:

[0052] 1. When the system scans the nth scan line 10, the potential is low (VS,L), leading first scan transistor T1, second scan transistor T2 and first switch transistor T5 to become on. As the potential of the nth emission line 30 is high (VE,H), connect transistor T4 and second switch transistor T6 are off. Thus, no current will pass through luminescence device 40 to prevent writing mistak...

embodiment 3

[0063] Refer to FIG. 3 for the circuit of a pixel of embodiment 3 in this invention. As the Figure shows, the driving circuit of each pixel on the display panel includes one scan line 10 and one data line 20. The driving circuit in this embodiment is about the same as that in Embodiment 1; however, the only difference is the source (S) of first switch transistor T5 is connected to voltage supply VDD instead of First voltage supply V1 and source (S) of second switch transistor T6 still connected to second voltage supply V2 as in Embodiment 1.

[0064] Actuation procedures of Embodiment 3 are described as follows:

[0065] 1. When the system scans the nth scan line 10, the potential is low (VS,L), leading first scan transistor T1, second scan transistor T2 and first switch transistor T5 to become on. As the potential of the nth emission line 30 is high (VE,H), connect transistor T4 and second switch transistor T6 are off. Thus, no current will pass through luminescence device 40 to preven...

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PUM

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Abstract

An active matrix display driving circuit is disclosed. Each pixel driving circuit includes one luminance device, one transistor connected to the device, one driving transistor and one storage capacitor. There are two switching transistors at one end of the storage capacitor connecting to two voltage levels for capacitive coupling and gate voltage of the driving transistor is changed. This driving circuit is applicable to the current driving pixel circuit of Poly-Si TFT EL display panel, improves image defects resulting from uneven threshold voltage of a TFT and IR drop and solves charging / discharging time problems for low current import.

Description

FIELD OF THE INVENTION [0001] This invention relates to a driving circuit of electro-luminescence device (EL device) is applicated in pixel of display. More particularly, the invention is directed to a driving device that improves the defect of images on an active matrix Poly-Si TFT EL device resulted from an inconsistent threshold voltage (Vth) and IR drop in addition to charging / discharging time problem. BACKGROUND OF THE INVENTION [0002] An EL device display can be classified according to its driving method, passive matrix (PM-EL Display) and active matrix (AM-EL Display). AM-EL display uses TFT (Thin Film Transistor) with a capacitor for storing data signals that can control EL display gray levels of brightness. [0003] The manufacturing procedure of a PM-EL display is simpler in comparison and less costly; however, it is limited in its size (<5 inches) because of its driving mode and has a lower-resolution display application. In order to produce an EL display with higher res...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G09G3/30
CPCG09G3/3241G09G2300/0842G09G2320/0233G09G2310/0251G09G2300/0861
Inventor WENG, RUEY-SHING
Owner WINTEK CORP